<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot>
      </slot>
    </div>
    <div class="dots">
      <span class="dot" :class="{active: currentPageIndex === index }" v-for="(item, index) in dots" :key="item"></span>
    </div>
  </div>
</template>

<script type="text/ecmascript-6">
import {addClass} from 'common/js/dom'
// 移动端滚动插件，可以作轮播图，
import BScroll from 'better-scroll'

export default {
  name: 'slider',
  props: {
    loop: {
      // 默认循环
      type: Boolean,
      default: true
    },
    autoPlay: {
      // 默认自动播放
      type: Boolean,
      default: true
    },
    interval: {
      // 多少毫秒滚动一次
      type: Number,
      default: 4000
    }
  },
  data () {
    return {
      dots: [], // 节点
      currentPageIndex: 0
    }
  },
  mounted () {
    // this.$nextTick(() => {
    //         this._setSliderWidth()
    //         this._initDots()
    //          if (this.autoPlay) {
    //   this._play()
    // }
    // })
    // 用户20秒无感，浏览器刷新一次17秒
    setTimeout(() => {
      this._setSliderWidth()
      this._initDots()
      this._initSlider()

      if (this.autoPlay) {
        this._play()
      }
    }, 20)
    // 适口改变的时候
    window.addEventListener('resize', () => {
      if (!this.slider) {
        return
      }
      this._setSliderWidth(true)
      // 宽度发生变化时刷新
      this.slider.refresh()
    })
  },
  activated () {
    if (this.autoPlay) {
      this._play()
    }
  }, // 销毁生命周期，销毁
  deactivated () {
    clearTimeout(this.timer)
  },
  beforeDestroy () {
    clearTimeout(this.timer)
  },
  methods: {
    // 横行滚动，设置宽度
    _setSliderWidth (isResize) {
      // 设置这个宽度
      this.children = this.$refs.sliderGroup.children
      let width = 0
      let sliderWidth = this.$refs.slider.clientWidth
      // 设置容器的宽度
      for (let i = 0; i < this.children.length; i++) {
        let child = this.children[i]
        addClass(child, 'slider-item')

        child.style.width = sliderWidth + 'px'
        width += sliderWidth
      }
      // 如果循坏
      if (this.loop && !isResize) {
        width += 2 * sliderWidth
      }
      this.$refs.sliderGroup.style.width = width + 'px'
    },
    _initSlider () {
      // 初始化BScroll
      this.slider = new BScroll(this.$refs.slider, {
        scrollX: true, // 横行滚动
        scrollY: false,
        momentum: false,
        snap: true,
        snapLoop: this.loop,
        snapThreshold: 0.3,
        snapSpeed: 400
      })

      this.slider.on('scrollEnd', () => {
        let pageIndex = this.slider.getCurrentPage().pageX
        if (this.loop) {
          pageIndex -= 1
        }
        this.currentPageIndex = pageIndex

        if (this.autoPlay) {
          clearTimeout(this.timer)
          this._play()
        }
      })

      this.slider.on('beforeScrollStart', () => {
        if (this.autoPlay) {
          clearTimeout(this.timer)
        }
      })
    },
    // 初始话就是length就是chidren的长度
    _initDots () {
      this.dots = new Array(this.children.length)
    },
    _play () {
      // pageIndex是第几个元素
      let pageIndex = this.currentPageIndex + 1
      if (this.loop) {
        pageIndex += 1
      }
      this.timer = setTimeout(() => {
        this.slider.goToPage(pageIndex, 0, 400)
      }, this.interval)
    }
  }
}
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
@import '~common/stylus/variable'

.slider {
  min-height: 1px;

  .slider-group {
    position: relative;
    overflow: hidden;
    white-space: nowrap;

    .slider-item {
      float: left;
      box-sizing: border-box;
      overflow: hidden;
      text-align: center;

      a {
        display: block;
        width: 100%;
        overflow: hidden;
        text-decoration: none;
      }

      img {
        display: block;
        width: 100%;
      }
    }
  }

  .dots {
    position: absolute;
    right: 0;
    left: 0;
    bottom: 12px;
    text-align: center;
    font-size: 0;

    .dot {
      display: inline-block;
      margin: 0 4px;
      width: 8px;
      height: 8px;
      border-radius: 50%;
      background: $color-text-l;

      &.active {
        width: 20px;
        border-radius: 5px;
        background: $color-text-ll;
      }
    }
  }
}
</style>